The engine needs different air intake volume under different revolving speed conditions. While the engine runs under low speed conditions, using a long inlet manifold can increase the air flow speed and pressure, which is conducive to the formation of intake vortex, oil and gas mixing and fuel atomization, thereby enhancing the torque. When the engine runs under high speed conditions, adapting a short intake manifold can shorten the admission stroke, increase the inertia of the air flow, smoothly promote the fresh gas into the cylinder and supply more fresh air to the engine, which is conducive for sufficient combustion in the cylinder and improvement of the output power. The opening and closing of the intake port of the side-ported rotary engine is controlled by the position of rotor side face during the rotation process. There is an abrupt structure in the intake port, so the valve-opening duration angle is small, the intake resistance is large and the charge coefficient is small, which is suitable for low speed conditions. However, the intake port of the peripheral-ported rotary engine is designed on the cylinder body directly, so the inlet airflow direction is generally not abrupt, the air resistance is small and the charge coefficient is large, which is suitable for high speed conditions. In addition, the rotary engine can achieve higher operating speed, so the revolving speed range is wide. Therefore, there are still some technical problems that need to be solved on how to design the intake manifold length, reasonably use the advantages of the side and peripheral-ported rotary engines, provide a suitable intake method and improve the engine intake efficiency under various operating conditions.
Therefore, for the above-mentioned related issues, it is necessary to design a composite intake mode with variable intake manifold to meet the different requirements of the air intake volume of the rotary engine.